1. Field of the Invention
The invention is directed towards late transition metal polymerization catalysts and their use in forming homopolymers from olefins or polar monomers and forming copolymers from olefins and polar monomers. In particular, the present invention relates to sulfur-containing and sulfur-nitrogen containing catalysts for the polymerization of olefins and polar monomers.
2. Description of the Related Art
Despite the technological and commercial success of Group 4 Ziegler-Natta and metallocene catalysts for polyolefins, the search for new catalysts and polymerization reactions continues. There is a drive to obtain even greater control over product properties and to extend the family of products to new monomer combinations. Catalysts that tolerate a variety of functional groups are of particular interest because they not only open up new product possibilities, but also allow for the use of cheaper, less pure monomer feeds. Late transition metal complexes are generally more tolerant of polar groups than those of early transition metals.
Late transition metal polyolefin catalysts have recently been reviewed (G. J. P. Britovsek, et al., Chem. Int. Ed., 1999, 38, 428; S. D. Ittel, et al., Chem. Rev., 2000, 100, 1169). To date, there are only a few examples of catalysts based on Group 11 metals (Cu, Au, Ag), which appeared only very recently in the literature. For example, Stibrany, et al. (PCT Pat. No. WO 99/30822) has disclosed LMX1X2 complexes, wherein M is Cu, Ag or Au, and L is a bidentate ligand, such as bis-benzimidazole, with activating cocatalysts for the homopolymerization and copolymerization of certain olefin and polar monomers. Copolymers of ethylene and certain polar monomers (e.g., alkyl acrylates, vinyl ethers) have been claimed. In PCT Pat. No. WO 98/35996 and Japanese Pat. No. 99171915, polymerization methods using CuXn, LCuXn, or L(Lxe2x80x2)CuXn catalysts with and without activating cocatalysts have been claimed. Specifically, these disclosures relate to Cu(II) amidinates, quinolates and acetoacetonates with MAO and other activators.
The rich coordination and redox chemistry of transition metal complexes with sulfur ligands provides a unique opportunity in the area of olefin oligomerization and polymerization. Metal complexes of sulfur-nitrogen chelating ligands have attracted considerable attention because of their interesting physicochemical properties and structural similarity to metalloprotein and metalloenzyme active sites. For example, it is known that histidine imidazole nitrogen atoms and methionine thioether sulfur atoms play key roles in the coordination of metals at the active sites of numerous metallo-biomolecules. Non-cyclic tetradentate chelating ligands with an NSSN-donor system are most utilized as models for such systems. An example for this type of ligand is the biomimetic N2S2 ligand, 1,7-bis(5-methyl-4-imidazolyl)-2,6-dithiaheptane (bidhp), which forms complexes like M(bidhp)X2, where M is Mn, Ni or Cu, and X is Br, Cl or NCS. In these complexes, the metal ions are hexacoordinated by two anions and the tetradentate ligand. The structures have distorted octahedral coordination.
Despite this broad range of activity on sulfur-containing complexes, those being reported as oligomerization and polymerization catalysts are extremely rare. The only known sulfur-containing polymerization systems based on a group 11 metal (Cu) have been disclosed by Hiraike, et al. (Japanese Pat. No. 200108119) and by Nishimura, et al. (Polym. Prepr., 1999, 40, 470), and both systems are free radical processes. In Japanese Pat. No. 200108119 to Hiraike, et al., radical polymerization of vinylic monomers using Cu(II)-thioether dihalide catalysts is disclosed. However, whether this system can polymerize olefins, such as ethylene, and copolymerize olefin and polar monomers are not mentioned. Living radical polymerization of styrene with a Cu bis(dithiocarbamate)/AIBN system have been disclosed by Nishimura, et al. (Polym. Prepr., 1999, 40, 470). It is not disclosed whether the system can polymerize olefins, such as ethylene, or whether it can tolerate polar monomers. Obviously, these systems fall in the category of free radical-initiated polymerization; and it is not clear whether they can polymerize or copolymerize olefins, such as ethylene and polar monomers.
Consequently, there remains a need for polymerization catalysts capable of forming olefinic polymers and copolymers and that are effective polymerization catalysts in the presence of polar monomers. Further, it is even more desirable to have a catalyst that can copolymerize olefin and polar monomers, forming functional copolymers.
It has been demonstrated by Wang, et al. (U.S. Pat. No. 6,120,692) that, under certain conditions, sulfur-containing complexes can tolerate contaminants (catalyst poisons), like H2S, H2O, C2H2, CO and H2. Therefore, another potential advantage of sulfur-containing polymerization catalysts is their resistance to poisons, which may potentially allow for the use of impure feeds.
It is one object of this invention to teach a catalyst system made from the combination of a complex having a formula selected from LMX1X2 or LMLxe2x80x2 and an activating cocatalyst. In either formula, L is a chelating ligand containing sulfur donors; M is a transition metal selected from either copper, silver, gold, manganese, iron, cobalt, palladium or nickel; X1 and X2 are independently selected from either halides, hydride, triflate, acetate, borate, alkyl, alkoxyl, cycloalkyl, cycloalkoxyl, aryl, thiolate, carbon monoxide, cyanate or olefins; and Lxe2x80x2 is a bidentate ligand selected from either dithiolene, dithiolate, diphosphine, bisimine, bispyridine, phenanthroline, oxolate, catecholate, thiolatoamide, thiolatoimine or thiolatophosphine. It is most preferred that Lxe2x80x2 is a dithiolene having the formula S2C2(CN)2.
In one embodiment, L has the formula RnZCS2, wherein R is either hydrogen, alkyl, substituted alkyl, alkenyl, substituted alkenyl, aryl, substituted aryl, alkoxyl, substituted alkoxyl, cycloalkyl, substituted cycloalkyl, amino or substituted amino groups; n=1 or 2; and Z is nitrogen or oxygen. If Z is oxygen, then n=1. Alternatively, if Z is nitrogen, then n=2; in this case, the preferred ligand L is iBu2NCS2.
In another embodiment, L is a bisimidazolyl dithioalkane ligand having the structure: 
In the structure shown above, R1, R2, R3 and R4 are independently selected from either hydrogen, alkyl, substituted alkyl, alkenyl, substituted alkenyl, aryl, substituted aryl, alkoxyl, substituted alkoxyl, cycloalkyl, substituted cycloalkyl, amino or substituted amino groups; and n=1 to 6. It is most preferred that L be either 1,7-bis(5-methyl-4-imidazolyl)-2,6-dithioheptane (bidhp) or 1,6-bis(5-methyl-4-imidazolyl)-2,5-dithiohexane (bidhx).
In a preferred embodiment, when X1=X2, each of X1 and X2 can be either bromine or chlorine.
Among the cocatalysts that may be used in the instant catalyst system, the preferred ones are alkylaluminoxanes, aluminum alkyls, aluminum halides, alkyl aluminum halides, Lewis acids other than any of the foregoing, alkylating agents and mixtures thereof. The most preferred cocatalyst is methylaluminoxane.
A further object of the present invention is to demonstrate that the sulfur/sulfur-nitrogen catalyst system taught herein may be successfully utilized to polymerize olefinic monomers under polymerization conditions. Preferred olefinic monomers are: acyclic aliphatic olefins; olefins having a hydrocarbyl polar functionality; and mixtures of at least one olefin having a hydrocarbyl polar functionality and at least one acyclic aliphatic olefin. For example, in addition to ethylene and acrylates, other monomers such as vinyl acetate, a-olefins, styrene and butadiene can also be polymerized.
It is believed that, under certain conditions, these systems can tolerate contaminants (i.e., are poison resistant), like H2S, H2O, C2H2, CO and H2. Hence, they can potentially allow for the use of impure feeds.
These sulfur-containing and sulfur/nitrogen-containing catalyst systems can be supported and used for gas-phase polymerization. Preferred supports include alumina, silica, mesoporous materials like MCM-41, and cross-linked polymers.
The catalyst system of this invention is the combination of a complex having the formula LMX1X2 or LMLxe2x80x2 and an activating cocatalyst. In either of the catalyst formulas, L is a chelating ligand containing sulfur donors. In one embodiment, L has the formula RnZCS2, wherein R is either hydrogen, alkyl, substituted alkyl, alkenyl, substituted alkenyl, aryl, substituted aryl, alkoxyl, substituted alkoxyl, cycloalkyl, substituted cycloalkyl, amino or substituted amino groups; n=1 or 2; and Z is nitrogen or oxygen. In particular, if Z is oxygen, then n=1. But, if Z is nitrogen, then n=2. In this embodiment, when n=2 and Z is nitrogen, the most preferred ligand L is iBu2NCS2, wherein iBu or i-Bu represents isobutyl.
In another embodiment, L is a bisimidazolyl dithioalkane ligand having the following structure: 
In this structure, R1, R2, R3 and R4 are independently selected from either hydrogen, alkyl, substituted alkyl, alkenyl, substituted alkenyl, aryl, substituted aryl, alkoxyl, substituted alkoxyl, cycloalkyl, substituted cycloalkyl, amino or substituted amino groups; and n=1 to 6. It is most preferred in this embodiment that L is either 1,7-bis(5-methyl-4-imidazolyl)-2,6-dithioheptane (bidhp) or 1,6-bis(5-methyl-4-imidazolyl)-2,5-dithiohexane (bidhx).
In further describing the formulas LMX1X2 and LMLxe2x80x2, M is a transition metal selected from either copper, silver, gold, manganese, iron, cobalt, palladium or nickel. M is most preferably copper, gold or silver.
X1 and X2 are independently selected from either halides, hydride, triflate, acetate, borate, alkyl, alkoxyl, cycloalkyl, cycloalkoxyl, aryl, thiolate, carbon monoxide, cyanate or olefins. Preferably, X1 and X2 are independently selected from either C1 through C12 alkyl, C1 through C12 alkoxyl, C3 through C12 cycloalkyl, and C3 through C12 cycloalkoxyl. In a preferred embodiment X1 is the same as X2, in which case each of X1 and X2 is either bromine or chlorine.
Continuing to describe the alternative formulas, Lxe2x80x2 is a bidentate ligand selected from either dithiolene, dithiolate, disphosphine, bisimine, bispyridine, phenanthroline, oxolate, catecholate, thiolatoamide, thiolatoimine or thiolatophosphine. The most preferred bidentate ligand Lxe2x80x2 is a dithiolene having the formula S2C2(CN)2.
Sample structures of catalysts having either formula LMX1X2 or LMLxe2x80x2 are: 
According to the present invention, a complex having the formula LMX1X2 or LMLxe2x80x2, wherein L, M, X1, X2 and Lxe2x80x2 are as previously defined, is combined with an activating cocatalyst. Examples of such cocatalysts include aluminum compounds containing an Alxe2x80x94O bond, such as the alkylaluminoxanes, including methylaluminoxane (xe2x80x9cMAOxe2x80x9d) and isobutyl modified methylaluminoxane; aluminum alkyls; aluminum halides; alkyl aluminum halides; Lewis acids other than any of the foregoing list; and mixtures of the foregoing can also be used in conjunction with alkylating agents, such as methyl magnesium chloride and methyl lithium. Examples of such Lewis acids are those compounds corresponding to the formula: Rxe2x80x3xe2x80x33 B, wherein Rxe2x80x3xe2x80x3 independently each occurrence is selected from hydrogen, silyl, hydrocarbyl, halohydrocarbyl, alkoxide, aryloxide, amide or combinations thereof, said Rxe2x80x3xe2x80x3 having up to 30 non-hydrogen atoms; and B is boron.
It is to be appreciated by those skilled in the art that the above formula for the preferred Lewis acids represents an empirical formula, and that many Lewis acids exist as dimers or higher oligomers in solution or in the solid state. Other Lewis acids which are useful in the catalyst compositions of this invention will be apparent to those skilled in the art.
Other examples of cocatalysts include salts of group 13 element complexes. These and other examples of suitable cocatalysts and their use in organometallic polymerization are discussed in U.S. Pat. No. 5,198,401 and PCT patent documents PCT/US97/10418 and PCT/US96/09764, all incorporated by reference herein. Preferred activating cocatalysts include trimethylaluminum, triisobutylaluminum, methylaluminoxane, ethylaluminoxane, chlorodiethyaluminum, dichloroethylaluminum, triethylboron, trimethylboron, triphenylboron and halogenated, especially fluorinated, triphenyl boron compounds.
Most highly preferred activating cocatalysts include triethylaluminum, methylaluminoxane, and fluoro-substituted triaryl borons, such as tris(4-fluorophenyl)boron, tris(2,4-difluorophenylboron), tris(3,5-bis(trifluoromethylphenyl) boron, tris(pentafluorophenyl) boron, pentafluorophenyl-diphenyl boron, and bis(pentafluorophenyl) phenylboron. Such fluoro-substituted triarylboranes may be readily synthesized according to techniques such as those disclosed in Marks, et al., J. Am. Chem. Soc., 113, 3623-25 (1991).
The catalyst system can be utilized by forming the metal complex LMX1X2 or LMLxe2x80x2 and, where required, combining the activating cocatalyst with the same in a diluent. The preparation may be conducted in the presence of one or more additional polymerizable monomers, if desired. Preferably, the catalysts are prepared at a temperature within the range from xe2x88x92100xc2x0 C. to 300xc2x0 C., preferably 0xc2x0 C. to 250xc2x0 C., and most preferably 0xc2x0 C. to 100xc2x0 C.
Suitable solvents include liquid or supercritical media, such as CO2, propane, butane, saturated and unsaturated hydrocarbons, N2 and NH3; straight- and branched-chain hydrocarbons, such as isobutane, butane, pentane, hexane, heptane, octane and mixtures thereof; cyclic hydrocarbons, such as cyclohexane, cycloheptane, methylcyclohexane and methylcycloheptane; halogenated hydrocarbons, such as chlorobenzene, dichlorobenzene and perfluorinated C4-10 alkanes; and aromatic and alkyl-substituted aromatic compounds, such as benzene, toluene and xylene. Suitable solvents also include liquid olefins that may act as monomers or comonomers, including ethylene, propylene, butadiene, cyclopentene, 1-hexene, 3-methyl-1-pentene, 4-methyl-1-pentene, 1-octene, 1-decene and 4-vinycylohexane (including all isomers alone or in mixtures). Other solvents include anisole, methylchloride, methylene chloride, 2-pyrrolidone and N-methylpyrrolidone. Preferred solvents are aliphatic hydrocarbons and aromatic hydrocarbon, such as toluene.
In the practice of this invention, it is believed that the cocatalyst interacts with the metal complex to create a polymerization-active metal site in combination with a suitable non-coordinating anion. Such an anion is a poor nucleophile, has a large size (about 4 Angstroms or more), a negative charge that is delocalized over the framework of the anion, and is not a strong reducing or oxidizing agent (S. H. Strauss, Chem. Rev., 93, 927 (1993)). When the anion is functioning as a suitable non-coordinating anion in the catalyst system, the anion does not transfer an anionic substituent or fragment thereof to any cationic species formed as the result of the reaction.
The equivalent ratio of metal complex to activating cocatalyst is preferably in a range from 1:10xe2x88x922 to 1:106, more preferably from 1:0.5 to 1:104, and most preferably from 1:0.75 to 1:103. In most polymerization reactions, the equivalent ratio of catalyst:polymerizable compound employed is from 10xe2x88x9212:1 to 10xe2x88x921:1, and more preferably from 10xe2x88x929:1 to 10xe2x88x924:1.
Advantageously, it is believed that the catalyst system of the present invention is not poisoned by compounds containing contaminants when used in the preparation of polymers and copolymers synthesized from olefinic monomers and polar monomers. Such contaminants include H2S, H2O, C2H2, CO and H2, among others. The result is that impure, cheaper feeds can be used to form polymers and copolymers.
The feeds used in the polymerization and copolymerization reactions disclosed herein typically are made up of olefinic monomers, polar monomers and mixtures thereof. Preferred olefinic monomers are acyclic aliphatic olefins, the most preferred of which is ethylene. Preferred polar monomers are n-butyl acrylate and t-butyl acrylate.
Olefinic monomers useful in forming homo- and copolymers with the catalyst of the invention include, for example, mono-olefins, non-conjugated dienes and oligomers, and higher molecular weight, vinyl-terminated macromers. Examples include C2-20 olefins, vinylcyclohexane, tetrafluoroethylene, and mixtures thereof. Preferred monomers include the C2-10 xcex1-olefins, especially ethylene, propylene, isobutylene, 1-butene, 1-hexene, 4-methyl-1-pentene and 1-octene or mixtures of the same.
Monomers having hydrocarbyl polar functionalities useful in forming homo- and copolymers with the catalyst of the invention are vinyl ether and C1 to C20 alkyl vinyl ethers, such as n-butyl vinyl ether; alkyl acrylates, such as C1 to C24 acrylates, especially t-butyl acrylate, and lauryl acrylate; and methacrylates, such as methyl methacrylate.
Other polar monomers that can be useful in the invention include vinyl acetate, vinyl pivalate, vinyl propionate, vinyl benzoate, vinyl chloride, acrylonitrile, acrylamide, isobutyl vinyl ether, methyl vinyl ketone, 1-vinyl-2-pyrrolidone, diethyl fumarate, acrylic acid, methacrylic acid, 5-norbornene-2-carboxylic acid, 5-norbornene-2-methanol, 3-vinylbenzoic acid, 2-acetyl-5-norbornene, 2-vinyl-1,3-dioxolane, 4-vinyl aniline, 4-vinylanisole, 4-acetoxystyrene, 4-vinylpyridine, 2-vinylpyridine, vinylcyclohexylamines, 1-vinylimidazole, N-vinylcaprolactone, 9-vinylcarbazole and vinyl acetic acid.
In general, the polymerization may be accomplished at conditions well known in the art for Ziegler-Natta or Kaminsky-Sinn type polymerization reactions, that is, temperatures from xe2x88x92100xc2x0 C. to 250xc2x0 C., preferably from 0xc2x0 C. to 250xc2x0 C., and pressures from atmospheric to 210 MPa (30,000 psig). Suitable polymerization conditions include those known to be useful for metallocene catalysts when activated by aluminum or boron-activated compounds. Suspension, solution, slurry, gas phase or other process conditions may be employed, if desired. The catalyst may be supported and such supported catalyst may be employed in the polymerizations of this invention. Preferred supports include alumina, silica, mesoporous materials, such as MCM-41, and polymeric supports, such as cross-linked polymers.
The polymerization typically will be conducted in the presence of a solvent. Suitable solvents include those previously described as useful in the preparation of the catalyst. Indeed, the polymerization may be conducted in the same solvent used in preparing the catalyst. Optionally, of course, the catalyst may be separately prepared in one solvent and used in another.
The polymerization will be conducted for a time sufficient to form the polymer, and the polymer is recovered by techniques well known in the art and illustrated in the examples hereinafter.
An important feature of the invention is the formation of substantially linear copolymers having the formula: 
where A is a segment derived from an acyclic aliphatic olefin of 2 to about 20 carbon atoms; R is H or CH3; X is xe2x88x92OR1 or xe2x88x92COOR1, wherein R1 is an alkyl group of 1 to 24 carbon atoms; and y is from about 0.02 to about 0.95, and preferably y is from about 0.18 to about 0.85. The polar content of the copolymer can be varied by reaction conditions as demonstrated in Examples 4 and 5.
These copolymers have polar functional monomer segments: 
which are substantially in the chain, rather than at the ends of branches.
In the case where xe2x80x94Axe2x80x94is a polymer segment derived from ethylene, the branch content is below about 20 branches/1000 carbon atoms, for example from about 0.5 to less than 20 branches.
The invention is further described in the following non-limiting examples.